DE10148650C1 - Fuel injection system for internal combustion engine with direct injection has fuel injection device having valve element on operating area and able to inject fuel directly into combustion chamber - Google Patents

Abstract

The invention concerns a fuel injection system for a direct injection internal combustion engine, comprising a fuel injection device (16) capable of directly injecting fuel in an internal combustion engine combustion chamber and having a valve closure (70). Said closure is adjacent to a working chamber (79), the position of the closure (70) depending on the pressure prevailing in the working chamber (79). A pressure multiplicator or demultiplicator piston (54) is adjacent on one side to a control chamber (96) and on the other to a high-pressure chamber (76). A fuel supply can apply different pressures to the control chamber (96). The invention is characterized in that in order to improve the emission behaviour of an internal combustion engine equipped with said direct fuel injection system, the multiplicator or demultiplicator piston (54) is integrated with the fuel injection device (16) and the high-pressure chamber (76) is integrated with the working chamber (79).

Description

State of the art

The invention relates to a fuel injection system for an internal combustion engine with direct injection, with a Fuel injector, which is the fuel directly into a combustion chamber of the internal combustion engine can inject and which has a valve element, which borders on a work area, the position of the Valve element depends on the pressure in the work area, with a Pressure booster piston, which on one side on one Control room and on the other side to a high pressure room limits, and with a fuel supply that the Apply different pressures to the control room can.

Such a fuel injection system is from DE 199 45 785 A1 known. With this is a fuel pump provided which a high pressure and a Has low pressure outlet. The high pressure outlet is with a control room of a pressure translation device connected. A high pressure room of the Pressure intensifier is via a check valve connected to the low pressure outlet of the fuel pump. A high pressure line leads from the high pressure room to one  Working space of a fuel injector, through which the pressure is transferred from the high pressure to this work area becomes. Depending on the pressure in the high pressure room or in the work room becomes a valve element of the fuel injector from a closed to an open position or reversed moves. The advantage of one Pressure translation device or a hydraulic Above all, the translation facility is one relatively simple fuel pump that can be used But fuel with very high pressure in one Combustion chamber of the internal combustion engine can be injected. This is especially for the favorable emission behavior of the Internal combustion engine important.

DE 197 38 804 A1 also describes a fuel Injection system with a hydraulic Translation device known. With him too hydraulic translation device via a High pressure line with the fuel injector connected.

The object of the present invention is to provide a fuel Injection system of the type mentioned above to further develop that when using the Emission behavior of the internal combustion engine even better and as little energy as possible to operate the fuel Injection system is required. The temperature should also the fuel injector during operation if possible be low.

This is the task of a fuel injection system at the outset that the Pressure booster piston in the fuel Injector and the high pressure space in the  Workspace are integrated.

Advantages of the invention

By integrating the pressure booster piston into the Fuel injector and the high pressure chamber in the work area is no longer a separate high-pressure line required by the pressure intensifier leads to the fuel injector. This will all of this from the pressure translation device too compressing volume reduced.

This accelerates the movement of the pressure booster piston in both directions, and subsequently the structure (and the Decrease) of the pressure in the high pressure room. This will in turn prevents fuel from starting or for example at the end of an injection only with low pressure or low momentum in the combustion chamber of the internal combustion engine arrives. The high impulse with which the fuel at the injected fuel injection system according to the invention leads to an improvement in emissions behavior the internal combustion engine.

Also those for the operation of the fuel Injection system energy is relatively low, because of the reduced volume that compresses and has to be relaxed, only lower energy losses occur with this compression and relaxation. This also reduces the undesirable heating of the fuel Injector during its operation, because less Entropy in the compression and decompression work of the Fuel is generated.

The funding volume, which is used for the compression of the  Fuel must be made available in the high pressure chamber, is lower, so having a fuel supply lower power can be provided. Furthermore the total loads on the fuel Injection system components used because the high pressure essentially only in the combined High pressure / work area is present. Therefore, cheaper Components for the production of the invention Fuel injection system can be used.

Advantageous developments of the invention are in Subclaims specified.

In a first further training it is proposed that the Pressure intensifier piston arranged coaxially to the valve element is. Such a fuel injection device builds All relatively compact in the radial direction.

In further training it is proposed that the Valve element is guided in the pressure booster piston. This has the additional advantage that the axial Fuel injector dimensions can be kept comparatively low. Furthermore, through the pressure intensifier piston a guide for the Valve element created so that this is very precise with cooperates with a valve seat assigned to it.

It is also advantageous if one in the valve element Longitudinal bore is present through which the high pressure space is supplied with fuel. This leads to another Reduction of the radial size of the fuel Injection device, which in the inventive Fuel injection system is used.  

In a particularly preferred embodiment of the fuel injection system according to the invention suggested that between the longitudinal bore in the Valve element and the high pressure chamber a check valve is present, which opens to the high pressure room. On such check valve is very simple to build and provides sure the high pressure space during compression is reliably disconnected from the fuel supply. This is very advantageous for the function of the pressure translator. The arrangement close to the high pressure room reduces the Loads on the longitudinal bore during operation, so that for the Valve element an inexpensive material can be chosen.

The longitudinal bore in the valve element can with a Low pressure fuel supply to be connected. So can the high-pressure room when there is no high pressure in it prevails, are supplied with fuel, which with even and low pressure is available. The The high-pressure chamber is thus filled with fuel evenly and safely, and the burdens of Longitudinal bore and thus the valve element are small held.

Alternatively, it is possible that the longitudinal bore in the valve element with a high pressure fuel supply which is also connected to the control room can apply different pressures. In this Case can on a separate low pressure Fuel supply can be dispensed with. This reduces the Cost of the fuel injection system according to the invention. Furthermore, the installation of this system in a Internal combustion engine facilitated because of the handling of a separate low pressure line is not required.  

In concrete terms, it is proposed that the Control room coaxially surrounds the valve element, and that the Longitudinal bore in the valve element via a radial running opening is connected to the control room. This is space-saving and inexpensive to manufacture.

In another variant, the Pressure intensifier piston via a spring on a nozzle body the fuel injector. This causes that the pressure booster piston reliably in its Starting position is applied.

One between the intensifier piston and the nozzle body existing and with a movement of the Pressure booster piston volume-variable cavity preferably via a check valve with a Leakage fluid outlet connected, the check valve opens to the leakage fluid outlet. In one Cavity, for example, the spring can be accommodated, which acts on the intensifier piston.

Through the leakage fluid outlet with the check valve in the first stroke of the pressure booster piston, if necessary, in the Cavity of existing fuel towards the leakage fluid outlet promoted. For all other strokes of the The pressure booster piston then only has to be in the Cavity remaining fuel vapor can be compressed and the one that may occur between the injections Leakage quantity conveyed to a leakage discharge line become. This will cause pressure fluctuations in the Low pressure cycle avoided and the energy expenditure again reduced, which for the operation of the fuel injection system according to the invention required is. As a result, the energy expenditure is reduced again,  which is used to operate the fuel Injection system is required.

It is also possible that the control room has a Check valve with a low pressure fuel supply is connectable, the check valve to the control room opens. If in operation the minimum pressure in the control room below that of the low pressure fuel supply provided pressure, is reached when the Minimum pressure in the control room opened the check valve and a small amount of fuel flows out of it Low pressure fuel supply in the control room.

This is based on the following consideration: That in the control room located fluid is from the high pressure Fuel supply constantly compressed and again relaxed. This creates entropy or heat, which leads to heating of the entire fuel Injector leads. This can work the fuel injector. By doing with the training proposed here constantly "fresh" and thus cool fuel from the low pressure Fuel supply gets into the control room, the Temperature of the fuel in the control room lowered and overall the heating of the fuel Injector in operation of the invention Reduced fuel injection system.

drawing

The following are particularly preferred Embodiments of the present invention under Reference to the attached drawing in detail explained. The drawing shows:  

Figure 1 is a schematic diagram of a first embodiment of a fuel injection system for an internal combustion engine with a fuel injection device.

FIG. 2 shows a partial section through the fuel injection device from FIG. 1 with a pressure booster piston in a first position;

Fig. 3 is a view similar to Figure 2 of a portion of the fuel injector of Figure 1 with the pressure booster piston in a second position..;

FIG. 4 shows a schematic diagram similar to FIG. 1 of a second exemplary embodiment of a fuel injection system for an internal combustion engine with a fuel injection device;

FIG. 5 shows a partial section through the fuel injection device from FIG. 4 with a pressure booster piston in a first position; FIG. and

Fig. 6 is a view similar to Figure 5 of a portion of the fuel injector of Figure 4 with the pressure booster piston in a second position..;

Description of the embodiments

In Fig. 1 a fuel injection system carries overall by reference numeral 10. It comprises a fuel tank 12 , from which a fuel pump 14 delivers the fuel to a fuel injection device 16 . This is an injector which injects the fuel directly into a combustion chamber 18 of an internal combustion engine (not shown further).

The fuel pump 14 includes a control pressure outlet 20 and a low pressure outlet 22 . A control pressure line 24 is connected to the control pressure outlet 20 . A control valve 26 is arranged in this. A control line 28 leads from the control valve 26 back to the fuel tank 12 . The control pressure line 24 leads to a control pressure connection 30 on the fuel injection device 16 . The control valve 26 is to be switched so that in one switching position the control pressure outlet 20 of the fuel pump 14 is connected to the control pressure connection 30 of the fuel injector 16 , whereas in another switching position of the control valve 26 the control pressure connection 30 is connected to the fuel tank 12 via the control line 28 is.

A low-pressure line 32 leads from the low-pressure outlet 22 of the fuel pump 14 to a low-pressure connection 34 on the fuel injection device 16 . A leakage fluid line 38 leads from a leakage fluid outlet 36 of the fuel injection device 16 back to the fuel tank 12 .

The exact structure of the fuel injection device 16 can be seen from FIGS. 2 and 3: Thereafter, the fuel injection device 16 comprises a nozzle body 40 , which consists of a lower part 42 in FIGS. 2 and 3 and one in FIGS 3 upper part 44 , and which is clamped by a nozzle clamping nut 46 against a connecting part 48 . The upper part 44 of the nozzle body 40 is sleeve-shaped. The lower part 42 of the nozzle body 40 has a step-shaped blind hole 50 . At the lower end of the lower part 42 of the nozzle body 40 in FIG. 2, outlet openings 52 lead from the blind hole 50 to the outside. All of the parts described so far are, moreover, rotationally symmetrical parts with a circular cylindrical cross section.

In the blind hole 50 of the lower part 42 of the nozzle body 40 and in the sleeve-shaped, upper part 44 of the nozzle body 40 , a pressure booster piston 54 is axially displaceable and received in the sliding play. This also consists of an upper part 56 and a lower part 58 in FIG. 2. An annular collar 60 is molded onto the lower part 58 of the pressure booster piston 54 at its upper end. A compression spring 62 is supported on the latter, the other end of which rests on the lower part 42 of the nozzle body 40 . The compression spring 62 acts on the lower part 58 of the pressure booster piston 54 with the annular collar 60 against a shoulder 64 in the upper part 44 of the nozzle body 40 . The compression spring 62 is received in an annular space 65 . A lower, axial end face 66 in FIG. 2 on the lower part 58 of the pressure booster piston 54 is overall smaller than an upper axial end face 68 in FIG. 2 on the upper part 56 of the pressure booster piston 54 .

The pressure booster piston 54 is penetrated by a recess. A section of a valve element is guided therein, which is designed as a valve needle 70 , which cooperates with a valve seat (without reference number) at the lower end of the blind hole 50 in the region of the outlet openings 52 . The valve needle 70 and the pressure booster piston 54 are thus arranged coaxially to one another. The valve needle 70 extends through the pressure booster piston 54 in FIG. 2 upwards into a blind hole 74 in the connection part 48 of the fuel injection device 16 . A compression spring 72 is tensioned between the upper end of the valve needle 70 in FIG. 2 and the end of the blind hole 74 , which presses the valve needle 70 against the valve seat in the region of the outlet openings 52 , that is to say in the closing direction.

The axial length of the lower part 58 of the pressure booster piston 54 is dimensioned such that the pressure booster piston 54 in the upper starting position shown in FIG. 2 ends downward before a cross-sectional tapering (without reference number) of the stepped blind hole 50 in the nozzle body 40 . An annular high-pressure space 76 is formed between the valve needle 70 , the lower end face 66 of the pressure booster piston 54 and the wall of the stepped blind hole 50 in the nozzle body 40 .

The valve needle 70 extends through the high-pressure space 76 . In the area of the high-pressure chamber 76 , a cross-sectional enlargement is present on the valve needle 70 , which forms a pressure surface 78 , the force resultant of which is opposite to the pressure force by the pressure spring 72, that is to say points in the opening direction of the valve needle 70 . The space surrounding the printing area is referred to as work space 79 . It coincides with the high pressure space 76 . An annular space (without reference number), which is formed between the valve needle 70 and the lower region of the blind hole 50 in the nozzle body 40 , leads from the high-pressure space 76 to the valve seat or the outlet openings 52 .

In the valve needle 70 , a radial bore 82 leads from a spring chamber 80 located in the valve needle 70 in the region of the high-pressure chamber 76 into the high-pressure chamber 76 . In the spring chamber 80, a spring-loaded check valve 84 is arranged which opens toward the spring chamber 80th A low-pressure channel 86 coaxial with the longitudinal axis of the valve needle 70 runs from the check valve 84 in the valve needle 70 to the upper end of the valve needle 70 in FIG. 2 and opens there into the blind hole 74 in the connecting part 48 . The blind hole 74 is connected via a radial bore 88 in the wall of the connecting part 48 to an annular channel 90 in a connecting part 92 . This creates a connection to the low-pressure line 32 via the low-pressure connection 34 .

From that of Fig. 2 located at the upper end of the connecting part 48 control pressure connection 30, a total of off-center control channel 94 leads to a control space 96. This control chamber 96 is formed as an annular space between the upper axial end surface 68 of the pressure booster piston 54 , the outer circumferential surface of the valve needle 70 and the upper part 48 of the nozzle body 40 and is thus arranged coaxially with the valve needle 70 . A spring-loaded check valve 98 , which opens towards the control chamber 96 , connects it to a flushing channel 100 , which opens into the radial bore 88 in the connecting part 48 .

In Fig. 3 the lower part of the fuel injection device 16 is shown. The view in FIG. 3 is rotated by 90 ° relative to FIG. 2 about the longitudinal axis of the fuel injection device 16 . Furthermore 3 is in Fig., The pressure intensifier piston 54 in its lower end position, whereas it in Fig. 2 in its upper starting position.

As can be seen from FIG. 3, a longitudinal groove 102 extends from the boundary region between the collar 60 at the lower part 58 of the pressure booster piston 54 and the shoulder 64 of the upper part 44 of the nozzle body 40 between the nozzle clamping nut 46 and the upper part 44 of the nozzle body 40 . It leads to a spring-loaded check valve 104 . This blocks towards the longitudinal groove 102 . A channel (not shown in the drawing) leads from the check valve 104 to the leakage fluid outlet 36 .

The fuel injection system 10 shown in FIGS. 1 to 3 operates as follows:
Before the fuel injection device 16 injects fuel into the combustion chamber 18 , the high-pressure chamber 76 is filled with fuel. For this purpose, fuel is delivered from the low pressure outlet 22 of the fuel pump 14 to the low pressure connection 34 of the fuel injection device 16 . From there, the fuel reaches the high-pressure chamber 76 via the low-pressure channel 86 in the valve needle 70 , the check valve 84 , the spring chamber 80 and the channel 82 . If the pressure in the high-pressure space 76 approximately corresponds to the pressure at the low-pressure outlet 22 of the fuel pump 14 , the check valve 84 closes.

The control valve 26 is initially switched so that the control pressure connection 30 of the fuel injection device 16 is connected to the fuel tank 12 . The control chamber 96 is therefore largely depressurized and the pressure booster piston 54 is in the upper starting position shown in FIG. 2. In order to carry out an injection, the control valve 26 is switched such that the control pressure connection 30 is connected to the control pressure outlet 20 of the fuel pump 14 . The corresponding pressure is now also present in the control chamber 96 via the control channel 94 . The pressure at the control pressure outlet 20 of the fuel pump 14 is considerably higher than the pressure at the low pressure outlet 22 .

For this reason and due to the area ratios of the axial end faces 66 and 68 of the pressure intensifier piston 54 a to the high-pressure chamber 76 towards directed force is obtained at the pressure intensifier piston 54, then the pressure booster piston that 54 moves in the direction of the high-pressure chamber 76th As a result, the fuel present in the high-pressure space 76 is compressed and a very high pressure is generated in the high-pressure space 76 . In the lower end position of the pressure booster piston 54 shown in FIG. 3, the pressure in the high-pressure chamber 76 can be up to approximately 1800 bar.

Due to the high pressure in the high-pressure chamber 76 or in the working chamber 79 , a force is exerted on the pressure surface 78 of the valve needle 70 in the opening direction of the valve needle 70 against the direction of action of the compression spring 72 . As a result of this force, the valve needle 70 is lifted off the valve seat, as a result of which the outlet openings 52 are connected to the high-pressure space 76 . The fuel thus enters the combustion chamber 18 at a very high pressure from the outlet openings 52 .

If the injection is to be ended, the control valve 26 is switched again such that the control pressure connection 30 of the fuel injection device 16 is connected to the fuel tank 12 . The control chamber 96 is thus suddenly relieved. The pressure booster piston 54 is pushed up again by the compression spring 62 ( FIGS. 2 and 3). As a result, the pressure in the high-pressure chamber 76 or in the working chamber 79 also drops, so that the valve needle 70 closes. If the pressure in the high-pressure chamber 76 has dropped far enough, the check valve 84 opens. This allows fuel to flow into the high-pressure chamber 76 through the low-pressure channel 86 .

Due to the sudden drop in pressure in the control chamber 96 , a relief pressure wave is generated. This causes the check valve 98 to open briefly and cold fuel to reach the control chamber 96 from the flushing channel 100 . This has the advantage that the temperature increase of the fuel enclosed in the control chamber 96 caused by the repeated compression and decompression is compensated for by the supply of cool fuel, and the temperature increase of the entire fuel injection device 16 can thus be kept within certain limits during operation.

Due to certain leaks between the parts moving relative to each other, fuel also enters that space 65 between the lower part 42 of the nozzle body 40 and the lower part 58 of the pressure booster piston 54 , in which the compression spring 62 is arranged. If the pressure booster piston 54 moves downward during an injection in FIGS. 2 and 3, the volume of this space also decreases. Fuel present in it is therefore discharged via the longitudinal groove 102 and the check valve 104 to the leakage fluid outlet 36 .

During the subsequent injections or stroke movements of the pressure booster piston 54 , essentially no more fuel is delivered from this space to the leakage fluid outlet 36 . Instead, fuel vapor forms in this space, which is compressed from vapor pressure to approximately ambient pressure during the stroke movements of the pressure booster piston 54 . This prevents pressure fluctuations in the low pressure circuit.

In Figs. 4 to 6 a second embodiment is shown of a fuel injection system 10. Such parts, elements and areas which have functions equivalent to parts, elements and areas of the exemplary embodiment shown in FIGS. 1 to 3 have the same reference symbols. They are not explained in detail here again.

An essential difference between the fuel injection system 10 shown in FIG. 4 and the previous system is that the fuel pump 14 has only one control pressure outlet 20 , but no low pressure outlet. Accordingly, only one control pressure connection 30 and one leakage fluid outlet 36 are also present on the fuel injection device 16 . In contrast, a low-pressure connection is missing in FIG. 5.

In the fuel injection device 16 shown in FIGS. 5 and 6, a check valve is missing between the longitudinal groove 102 and the leakage fluid outlet 36 . Instead, the longitudinal groove 102 leads directly to the leakage fluid outlet 36 via a leakage channel 106 . This is also connected via a radial bore 108 in the wall of the connection part 48 to the interior of the blind hole 74 in the connection part 48 .

In the fuel injection device 16 shown in FIGS. 5 and 6, the high-pressure chamber 76 is supplied with fuel via the control chamber 96 . For this purpose there is a radial inlet bore 110 in the wall of the valve needle 70 at the level of the control chamber 96 . The channel 86 in the valve needle 70 also extends from the check valve 84 only up to the level of the control chamber 96 . The advantage of this exemplary embodiment is that a low-pressure system (low-pressure outlet on the fuel pump, low-pressure line, low-pressure connection on the fuel injection device, etc.) can be dispensed with.

As stated above, the high-pressure space 76 is the space in which an enclosed fluid is compressed by the pressure booster piston 54 and a very high pressure is thus generated. When the working chamber 79 is that space is created in the pressure change to the pressure surface 78 of the valve needle 70 a force which leads to a movement of the valve needle 70th In both fuel injection devices 16 described above, the high-pressure space 76 of the pressure booster piston 54 is integrated into the working space 79 of the valve needle 70 . The two rooms therefore coincide. Thus, only a comparatively small volume is compressed overall during an injection by the fuel injection device 16 , which reduces undesirable elasticity effects of the fuel enclosed in the high-pressure chamber 76 .

Claims (11)

1. Fuel injection system ( 10 ) for an internal combustion engine with direct injection, with a fuel injection device ( 16 ) which can inject the fuel directly into a combustion chamber ( 18 ) of the internal combustion engine and which has a valve element ( 70 ) which is connected to a working space ( 79 ), the position of the valve element ( 70 ) depending on the pressure in the working space ( 79 ), with a pressure booster piston ( 54 ) which on one side to a control chamber ( 96 ) and on the other side to a high pressure space ( 76 ), and with a fuel supply ( 14 ) which can pressurize the control chamber ( 96 ) with different pressures, characterized in that the pressure booster piston ( 54 ) into the fuel injection device ( 16 ) and the high pressure chamber ( 76 ) into the working chamber ( 79 ) are integrated. 2. Fuel injection system ( 10 ) according to claim 1, characterized in that the pressure booster piston ( 54 ) is arranged coaxially to the valve element ( 70 ). 3. Fuel injection system ( 10 ) according to claim 2, characterized in that the valve element ( 70 ) is guided in the pressure booster piston ( 54 ). 4. Fuel injection system ( 10 ) according to one of claims 2 or 3, characterized in that in the valve element ( 70 ) there is a longitudinal bore ( 86 ) through which the high-pressure chamber ( 76 ) is supplied with fuel. 5. Fuel injection system ( 10 ) according to claim 4, characterized in that between the longitudinal bore ( 86 ) in the valve element ( 70 ) and the high pressure chamber ( 76 ) there is a check valve ( 84 ) which opens towards the high pressure chamber ( 76 ) , 6. Fuel injection system ( 10 ) according to one of claims 4 or 5, characterized in that the longitudinal bore ( 86 ) in the valve element ( 70 ) is connected to a low-pressure fuel supply ( 22 ). 7. Fuel injection system ( 10 ) according to one of claims 4 or 5, characterized in that the longitudinal bore ( 86 ) in the valve element ( 70 ) is connected to a control pressure fuel supply ( 20 , 26 ), which also the control chamber ( 96 ) can apply different pressures. 8. Fuel injection system ( 10 ) according to claim 7, characterized in that the control chamber ( 96 ) coaxially surrounds the valve element ( 70 ), and that the longitudinal bore ( 86 ) in the valve element ( 70 ) via a radially extending opening ( 110 ) is connected to the control room ( 96 ). 9. Fuel injection system ( 10 ) according to one of the preceding claims, characterized in that the pressure booster piston ( 54 ) is supported via a spring ( 62 ) on a nozzle body ( 40 ) of the fuel injection device ( 10 ). 10. Fuel injection system ( 10 ) according to claim 9, characterized in that between the pressure booster piston ( 54 ) and the nozzle body ( 40 ) existing and upon movement of the pressure booster piston ( 54 ) volume variable cavity ( 65 ) via a check valve ( 104 ) is connected to a leakage fluid outlet ( 36 ), the check valve ( 104 ) opening towards the leakage fluid outlet ( 36 ). 11. Fuel injection system according to one of the preceding claims, characterized in that the control chamber ( 96 ) via a check valve ( 98 ) can be connected to a low-pressure fuel supply ( 22 ), the check valve ( 98 ) opening towards the control chamber ( 96 ) ,